Tool for abrasive purposes.



m. 635,346; Patented 0a., 24, I899.

5. s. PAPPRILL. Tom. FOB ABRASIVE PURPOSES.

(Application filed Feb. 8, 1899.) (No Model.) 3 Sheets-Shoat I.

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n6. 635,346. Patented oat; 24, I899.

ms. PAPPBILL. .TOOL FOR ABRASIVE PURPOSES.

(Application filed Feb. 8, 1899.)

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(No Model.)

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No. 635,346. Patented Oct. 24, I899.

' R. S. PAPPRILL.

TOOL FOR ABRASIVE PURPOSES.

(Application filed m). s, 1899.)

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PATENT me D RUDOLPH S. PAPPRILL, OF DETROIT, MICHIGAN.

TOOL FOR ABRASIVE PURPOSES.

SPECIFICATION forming part of Letters Patent No. 635,346, dated October24, 1899.

To CLZZ whom it may concern.-

Be it known that I, RUDOLPH S; PAPPRILL, a subject of the Queen of GreatBritain, residing at Detroit, county of Wayne, State of Michigan, haveinvented a certain new and useful Improvement in Tools for AbrasivePurposes; and I. declare the following to be a full, clear, and exactdescription of the invention, such as will enable others skilled in theart to which it pertains to make and use the same, reference being hadto the accom= panying drawings, which form a part of this specification.

This invention relates to tools for grinding cylindrical and othersurfaces, and has for its object a tool which'may be used to grind ortrue up revolving cylindrical surfaces by employing the tool while thecylinder is rotating. It is especially useful in truing up and keepingtrue the commutators of motors and dynamos.

The commutators of motors and dynamos of the style now in common usethroughout the country become through use and the action of the currentirregular and out of true as cylinders or disk circles by wearing awayof those parts of the commutator-segments that come under the abradingaction, the brushes, and the tearing effect of sparking. The difficultyconsists not only in the destruction of the copper segments of thecommutator, but also in the embedding of small particles of copper inthe insulating non-metallic material between the segments, therebyestablishing a complete or partial short circuit between differentsegments composing the comin utator. This difficulty is caused byembedding small particles of copper in the insulating non-metallic partof the commutator so closely that they eventually form a continuousmetallic band across the insulating-space, allowing the flow of acurrent between two contiguous sections of the commutator. This troubleis so common that it becomes necessary to dress off the commutator quitefrequently, and this is generally done by using an abrading material ortoolsuch as sandpaper, emery-paper, or a file-Which is held againstthesurface of the commutator while it is in motion. In course of timecommutators thus treated become more and more irregular andout of true,and it finally becomes 7 Application filed February 8 1899. Serial No.704,897. (No model.)

necessary to remove the commutator and turn it off in a lathe. The toolwhich is the subject of this invention can be employed at any time whilethe commutator is running and without requiring other motive powerapplied to the motor or dynamo than that which is used to produce itsordinary motion, and the work of the tool is such that not only is thetrouble spoken of removed, but the commutator continues trulycylindrical and need never be removed until so much has been cut awaythat it may be considered worn out.

In principle the tool consists of a number of abrading-blocks orgrinding-blocks, which are arranged to be held with their grindingfacesin proper position to do the desired work. If the tool is used to trueup a cylinder, the grinding-faces are held in the arc of a circle ofwhich the center is at the center of the commutator or cylinder. Thetool thus constructed can be employed in such a way that oneabrading-block steadies another, and thus produces that accuracy inholding the toolup to its workwhich is necessary to produce thetrue-cylindrical surface desired in the commutator.

In the drawings, Figure 1 is a side view of the tool, and in this figurethe tool is shown as applied to the commutator. Fig. 2 is a plan View ofthe tool. The position of the commutator beneath the tool is indicatedin this figure also. Fig. 3 is a side elevation of a tool of a largersize and having an arrangement for the use of both hands in holding it.Fig. at is a cross-sectionof one of the abrading-blocks. Fig. 5 is aside elevation, partly in section, and shows a means for changing theradius of the inner are passing through the inner faces of theabrading-blocks that differs from the means for producing suchadjustment shown in Figs. 1, 2, and 3. Fig. 6 is a cross-section at theline a; 00 of Fig. 5. Fig. 7 shows a form of the tool in which thehandle is arranged parallel with the long axis of the cutting-block.

The handle of the tool isindicated at A, and in the handle A is inserteda tang C of a fork B. At each end of the fork B is a screwthreaded hole,through which engages a winged screw L. Midway between the ends and ateach side of the fork is a lug b, provided with a hole for theengagement there- Ibo through of a holding-bolt c. The abradingblocksare held to the fork mediately in the following way:

G indicates a strip of flexible material, not only flexible butresilient. The flexible strip G is bent to a curvature approximating toa curve concentric with the cylinder that the tool is to be employedupon. Along the inner face of the strip G the ends of the strip placed astrip 9 of insulating material. A number of abrading-blocks are seated.The

two outer abrading-blocks II and II are turned against the inturnedterminals of the insulating-strip g. Another abrading-block is placedintermediate the extreme, (or there may be more than one intermediateblock.) Each of the blocks H, 850., is provided with a holding-screw 71,partially embedded in it and having a projecting screw-threaded tangwhich engages through the strips G g and is held to the strips by a nuth, which is run onto the projecting end of the screw it. Theintermediate abrading-block (or blocks) is spaced from the end blocks byspacing-blocks J, of insulating material, and these spacingblocks areheld in place by small screws 7t, that pass through the strips G 9 intothe blocks J. The blocks J nearly fill the space between theabrading-blocks II, &c.; but they are, however, enough shorter than thespace they are set into to allow the requisite variation or adjustmentof curvature of the strips G g. -At the end of the strip G are abntmentsagainst which the ends of the setserews engage.

In the larger form of tool shown in Fig. 3 the handle A instead of beingshown in the forks midway between their ends is at one side of themiddle point, and at the other side of the middle point, between theends of the forks, is a second handle A as shown in the drawings. Thissecond handle has the form of a loop orear, and the grip part of thehandle lies substantiallyparallel with the body of the prongs of thefork. The form or shape of either handle is not material either to theinvention or to the usefulness of the tool.

In Fig. 5 a different means of adjusting the curvature to theholding-strips isshown. In the form of tool shown in this figure thepressure is produced by changing the position of the end of a leverwhich bears against the fixed part of the handle A and against a fixedpoint on the strip. Levers P I are socured by pins or joined connectionsto the strips at points that are approximately at equal distance ateither side of the middle line. The free ends of the levers P engage ina scroll groove u, that is cut in the face of a rotatable washer N. Thewasher being on the tang of the tool, the rotation of the washer changesthe position of the free ends of the lever P P and adjusts the strip G.

The abrading-lolocks H, &c., are composed of any suitable abradingmaterial-such as oorundum, emery, crushed quartz, or even some timessharp sand-and such material is generally a poor conductor ofelectricity, so that the insulating-strip g might be omitted and thetool still do its work. Such a tool Without an insulating-strip would bejust as efficient for abrading purposes as a tool which is provided withan insulating-strip; but the insulatingstrip is interposed as a measureof precaution, and the bolt or screw h, one part of which is sunk intothe abrading-block, should also be insulated from the part ,G by meansof proper bushings and washers, as indicated at w and a; in Fig. 4-.

In using the tool selection is made of one that has a curvatureapproximately right for the cylindrical surface which is to be treated,and the curvature is adjusted by means of screws until the propercurvature is attained. The tool is held against the revolving commutatoruntil the defects of the armature are cured. In the course of time theblocks Wear away, as they are generally purposely made quite soft, andas they wear away and as the com in utatorcylinder becomes smaller thetool is readjusted from time to time to meet the changed conditions.

\Vhat I claim is 1. In a tool for grinding cylindrical and othersurfaces, the combination of a plurality of abrading-blocks, and aflexible strip on which said abrading blocks are mounted, substantiallyas described.

2. In a tool for grinding cylindrical and other surfaces, thecombination of abradingblocks,a flexible strip on which saidabradingblocks are held, means for holding the flexible strip and meansfor adjusting the curvature thereof, substantially as described.

In a tool for grinding cylindrical and other surfaces, the combinationof abradingblocks, spacingblocks located between adjacentabrading-blocks, a flexible strip adapted to be bent, and means forproducingacurvature of said strip, substantially as described.

4. In a tool for grinding cylindrical and other surfaces, thecombination of a flexible strip, abrading-blocks held thereto, means forinsulating the blocks, from the strip, and from each other, and meansfor adjusting the flexible strip to a desired curvature, substantiallyas described.

In testimony whereof I sign this specification in the presence of twowitnesses.

RUD OIIPI'I S. PAIPRILL.

\Vitnesses:

J. N. GooDnIcH, MARION A. Rnnvn.

